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Employee Stock And Incentive Plan (Assumptions Used In The Pricing Model - Performance Stock Units) (Details) (Performance Share Units [Member], USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	3 years	3 years
Risk-free interest rate	0.40%	1.20%
Expected volatility	22.10%	29.70%
Grant date fair value per option	$ 23.89	$ 24.38

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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